Hillary Clinton has a lead of nearly 230 pledged delegates — and with each passing week, it’s becoming increasingly unlikely that Senator Sanders will be able to catch up. In order to do so, Sanders has to win the four remaining delegate-rich primaries — New York, Pennsylvania, California, and New Jersey — with roughly 60 percent of the vote. To put that in perspective: Sanders has thus far won only two primaries with that margin: Vermont and New Hampshire. Needless to say, the size and demographic makeups of New York, Pennsylvania, California, and New Jersey are decidedly different than Vermont and New Hampshire. And these figures don’t even include superdelegates, where Clinton has an overwhelming lead.

Here's that paragraph visualized:

(Philip Bump / The Washington Post)

That Clinton lead may not look all that daunting until you remember this: There are no winner-take-all primaries or caucuses on the Democratic side. Every contest allocates delegates proportionally. What that means in simple terms is that it's hard for a front-runner to pull away and very hard for an underdog to close the gap.

Here's another way to think about Wisconsin vis-a-vis the New York primary in two weeks time, courtesy of our own Philip Bump:

To overcome Clinton's pledged delegate lead, Sanders has to win big states BIG. As Mook notes, Sanders needs to win 60 percent (or higher) of the vote in New York, Pennsylvania, New Jersey and California. Possible? Sure. Likely? Not even close -- especially when you consider (as Mook does) that the only two states where Sanders has achieved that margin are his home state and one that directly borders it.